PB2257: SARS-COV-2 VARIANTS DETECTED IN EMPLOYEES OF ONE MEDICAL CENTER
Authors: B. Biderman, O. Gavrilina, O. Glinstchikova, T. Makarik, I. Fevraleva, D. Tikhomirov, T. Tupoleva, A. Sudarikov
Journal: HemaSphere (2022)

Background: March 2020 strict measures were introduced at the National Research Center for Hematology (Moscow, Russia) in order to prevent the spread of SARS-CoV-2: the mandatory wearing of masks, screening for the presence of symptoms of acute respiratory viral infections, regular PCR testing of all staff and patients, a ban on visiting patients, and cancellation of all face-to-face meetings of the employees. Nevertheless, in the fall of 2020, an outbreak of the disease among employees was detected in the institution. Aims: To study the variety of SARS-CoV-2 variants infecting employees during the outbreak and to reveal possible transmission routes. Methods: The study included 42 employees infected during the 09/17/2020 - 01/01/2021 outbreak, which corresponded to the 2nd wave of COVID-19 worldwide. PCR testing for the detection of SARS-CoV-2 RNA in nasopharyngeal samples from the staff of the center was performed using the PCR-RV-2019-nCov kit (Syntol, Russia). Sequencing of SARS-CoV-2 samples was performed by the NGS method using the QIAseq SARS-CoV-2 Primer Panel kit (Qiagen, USA); the raw data were analyzed according to the HAVOC protocol (DOI 10.1186/s12859-021-04294-2). Results: Only 4 (10%) out of 42 employees had a positive PCR test result while having COVID-19 symptoms, the rest - during routine screening. The course of disease was characterized as asymptomatic in 2 (5%), mild in 28 (86%), moderate in 3 (7%), severe in 1 (2%), extremely severe was not detected. Based on sequencing data, we identified 5 different variants of SARS-CoV-2 found in 2 or more samples. Four of them were found each within only one clinical department and did not occur outside of it. Variant 1 was first detected in an asymptomatic carrier on 10/29/2020 and again on 11/2/2020 simultaneously in 8 employees during routine testing (a total of 13 cases were registered in one department). This type was distinguished by the presence of 5 missense mutations in the Spike region, which may have been the reason for its high contagiousness. Among these 13 employees, 1 (7%) had a severe infection, 2 (14%) had a moderate infection, 9 had a mild course (1 had a cutaneous form), and 1 (7%) had an asymptomatic infection. Variant 2 was detected in 2 carriers, variants 3, 4 - in 3, with an interval of a week. Variant 5 was identified in 4 employees from 2 departments (2 people in each from 10/8/2020 to 10/26/2020). For these employees, the course of COVID-19 was characterized as mild. Also, 3 pairs of similar variants were identified, however, the lack of complete similarity and a large time interval raises doubts about their connection. All other 11 SARS-CoV-2 nucleotide sequences were unique. Summary/Conclusion: Anti-epidemic measures taken at the center have shown effectiveness in reducing the spread of nosocomial infection. The identified clustering of virus variants indicates the predominant infection of employees within departments. The obtained clinical data do not make it possible to identify associations of a particular SARS-CoV-2 variant with the course of the disease. Sequencing of SARS-CoV-2 samples allowed for an epidemiological study and identification of a variant that is likely to be highly contagious.